1. Field of the Invention
The present invention generally relates to an injection mold, a production method thereof, a production system thereof, a designing apparatus and a designing computer program thereof, an injection method, a molded component, and an optical system therewith, and specifically relates to an injection mold of precision components such as a plastic lens, a production method thereof, a production system thereof, a designing apparatus and a designing computer program thereof, an injection method using the injection mold, a molded component produced by the injection mold, and an optical system that is equipped with an optical component that includes the molded component.
2. Description of the Related Art
Optical components, such as a lens, are often made of resin, such as plastics, due to a low cost and lightweight. Most of the optical components are produced by an injection molding, and the like. A method of the injection molding uses an injection mold that has a cavity in a shape according to a product to be produced. A surface of the molding part is processed such that the cavity can be formed based on the shape of the product (design shape).
Then, melted and pressurized resin is injected to the cavity of the mold using an injection molding machine, and the like. After the resin is cooled, solidified resin is separated from the mold, and the product of the shape according to the surface shape of the molding part is obtained.
As for the resin for the injection molding, thermal plastics, such as amorphous polyolefin resin and acrylic resin (PMMA), are often used in the case of production of optical components. The resin is heated to 200 degrees C. or higher to be melted, and is injected to the injection mold while it is melted. For this reason, the molded product is subject to contraction when the injected resin solidifies, and further cooled to room temperature. Dimensions of the product tend to be smaller than the dimensions of the mold cavity. Then, in order to compensate the contraction, the contraction is estimated in advance by approximating the contraction by an inverse of isotropic deformation ratio (contraction ratio), and is applied to design of the cavity, i.e., the surface of the molding part.
The optical components are widely applied to a laser beam printer, a digital reproducing machine (copying machine) and the like, in view of economical prices. Recently, a demand for a high quality image has been increasing, which requires a high precision of the optical components used in an optical scanning system that greatly influences the image quality, while keeping the low costs. Therefore, a demand for a high precision and a low cost plastic optical component is increasing.
A product molded by the injection molding contains an uneven internal stress due to an unevenness of a cooling speed, an unevenness of resin temperature, and an asymmetry of the shape of the product. The internal stress causes an uneven deformation (strain). Further, a production error of the molding part cannot be disregarded. For these reasons, an actual deformation of the products is caused not only by a proportional contraction, but also by other periodical deformations that contain various frequency components. Therefore, it has been difficult to produce a high precision molded component that satisfies required properties (such as optical properties) by designing the cavity and the surface in precaution of only the isotropic contraction. This indicates that a process and a production method that consider various deformations occurring in the molded component are desired, such that a molded component that realizes designed properties is produced.
In order to control dimensions and a sphere of the molded component within predetermined tolerances, a practice has been that the shape of the molded component is measured to obtain shape data, the shape data is compared with designed dimensions, errors are determined, and the surface of the molding part is processed to correct the errors.
For convenience of computer processing, a polynomial (a shape regression) is widely used to approximate an amount of compensation from the shape data, because processing and production of the molded part are often performed by a processing apparatus managed and controlled by a computer. This approximation process not only interpolates values at an unmeasured point, but also extracts a low frequency component (a long wavelength component), that is, it has a low pass filter effect.
However, sometimes, designed properties were not obtained even after correcting the errors based on the long wavelength component contained in the shape data. Then, studies were made about shorter wavelength components (undulations).
For example, Japanese Laid-Open Patent Application No. 2000-263391 (hereinafter referred to as the first public knowledge) reveals a method in which a wavelength of a representative undulation component of a molded component is obtained, and removed. This method does not use a process of acquiring data from a polynomial, such as the shape regression, but performs a frequency analysis, such as the Fourier analysis, and extracts the undulation component.
Further, Japanese Laid-Open Patent Application No. 2001-62871 (hereinafter referred to as the second public knowledge) reveals a method of acquiring a compensation amount by a shape formula (a polynomial or a shape regression) that expresses a simulated figure considering a contraction ratio, and by extracting an undulation component.
Furthermore, Japanese Patent Publication No. 2898197 (hereinafter referred to as the third public knowledge) reveals a molding method that offsets shape errors, based on an approximation formula of a polynomial. In applying the approximation formula, an optically functional area of an optical component produced under stable molding conditions is divided into a plurality of areas. Then, the formula is applied to each of the areas, and continuity is provided to each boundary of the areas.
The first public knowledge is capable of identifying a wavelength of a governing undulation component, however, it is not capable of separating the undulation component from the shape of the molded component, and it is not capable of extracting sufficient information regarding an amplitude of the undulation component. For this reason, the first public knowledge cannot be applied to a method that provides a compensation amount varying from point to point in a corrective process. The first public knowledge uses elasticity and viscosity of a processing tool in order to remove the undulation component. However, in the case of processing a surface with varying curvatures, a concordance of a processing tool with an object of the process is a prerequisite. That is, the elasticity of the processing tool has to be low, which causes an insufficient removal of the undulation component. The second public knowledge considers a comparatively short wavelength component that is not included in a conventional shape regression, however, there is a possibility that a compensation amount contains an unnecessary high frequency component that is irrelevant to properties (such as optical properties) that are to be enhanced. This causes a process to become unstable and inefficient, depending on response characteristics of a processing apparatus. Further, this method applies a uniform contraction ratio regardless of wavelength, and for this reason, accuracy at an important wavelength tends to be low.
In FIG. 31, an example is presented, where the molded component is a scanning lens of a polygon scanner optical system of a laser beam printer. The polygon scanner optical system shown in FIG. 31 includes a semiconductor laser S1 as a light source, a collimator lens S2, a polygon mirror S3, a scanning lens S4, and a photo conductor S5. A light flux emitted from the semiconductor laser S1 passes through the collimator lens S2, and irradiates the polygon mirror S3. The light flux is deflected by rotation of the polygon mirror S3, passes through the scanning lens S4, and is focused near an image surface where the photo conductor device S5 is located.
If a shape error S6 is present in the surface of the scanning lens S4, a focal deviation S7 will arise in the image surface, due to a local lens effect of the shape error S6. If an amount of the focal deviation S7 is large, a beam spot is blurred at the image surface, causing picture quality degradation. Here, a relationship between a space wavelength of the shape error S6 and the focal deviation S7 is examined, where amplitude of the shape error S6 is assumed constant.
As the first case, the space wavelength of the shape error S6 is supposed to be sufficiently longer than a diameter D of the light flux that passes through the scanning lens S4. Then, since the curvature of the lens is small for the long wavelength, the amount of the focal deviation is small.
As the second case, the space wavelength of the shape error S6 is supposed to be sufficiently shorter than the diameter D of the light flux. In this case, the curvature of the lens for the short wavelength may be large, however, an optical effect of the curvature is averaged within limits of the diameter D of the light flux. As a result, the amount of the focal deviation is small.
As the third case, the space wave length of the shape error S6 is supposed to be similar to the diameter D of the light flux. In this case, the curvature is large, and the averaging effect cannot be expected. Therefore, the focal deviation in this case is larger than that of the first case and the second case. In summary, when the space wavelength of the shape error S6 that is present on the surface of the scanning lens S4 is similar to the diameter D of the light flux that passes through the scanning lens S4, an influence of the shape error to the amount of focal deviation is the greatest, causing a significant deterioration of the image quality.
For reasons such as above, there are many cases where a larger tolerance is allowable for a longer wavelength, however, a stricter tolerance should be observed for a shorter wavelength. For example, in the case of a 100 mm long lens, a 1xcexcm tolerance may be given to a wavelength component of 50 mm, while only 0.05 xcexcm tolerance can be allowed to a wavelength component of 1 mm.
The third public knowledge has a problem that an accurate feedback to processing data of short wavelength components, such as undulations, contained in the shape error is difficult. Further, the third public knowledge does not consider the contraction ratio, causing insufficient removal of the error. With demands for a high image quality of the laser printers and the like, optical components that surely realize designed performances are needed. It is envisaged that the conventional methods will not be able to meet the demands.
It is a general object of the present invention to provide an injection mold, a production method thereof, a production system thereof, a designing apparatus and a designing computer program thereof, an injection method, a molded component, and an optical system therewith that substantially obviate one or more of the problems caused by the limitations and disadvantages of the related art.
Features and advantages of the present invention will be set forth in the description which follows, and in part will become apparent from the description and the accompanying drawings, or may be learned by practice of the invention according to the teachings provided in the description. Objects as well as other features and advantages of the present invention will be realized and attained by The present invention generally relates to an injection mold, a production method thereof, a production system thereof, a designing apparatus and a designing computer program thereof, an injection method, a molded component, and an optical system therewith particularly pointed out in the specification in such full, clear, concise, and exact terms as to enable a person having ordinary skill in the art to practice the invention.
More specifically, the objectives of the present invention are offering:
a production method and a production system that produce an injection-mold that is suitable for producing a molded component that surely realizes designed properties;
an injection mold that is capable of stably producing the molded component that surely realizes the designed properties, and a molding method using the injection mold;
a designing apparatus and a designing computer program that enable designing of the injection mold that is suitable for producing the molded component that surely realizes the designed properties;
a molded component with excellent component properties, and an optical component with excellent optical properties; and
an optical system that has excellent scanning accuracies.
To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention provides the injection mold, the production method thereof, the production system thereof, the designing apparatus and the designing computer program thereof, the injection method, the molded component, and the optical system therewith, as follows.
The present invention provides the production method of an injection mold that has a mold cavity of a predetermined shape, surface shape of the cavity being copied to a molding material such that a molded component is produced, wherein a first process extracts a plurality of wavelength components of shape errors contained in the molded component based on at least one of the surface shape of the cavity of a first molding part and the molded component produced by the first molding part, and a second process generates processing information that is used in processing the surface shape of the cavity of a second molding part such that an amount of at least one of the wavelength components of the shape errors is reduced.
Here, the first molding part and the second molding part may be physically different objects, or the first molding part that has been reworked according to the above process may be made the second molding part.
At the first process, the plurality of the wavelength components that give adverse affects to the properties of the molded component are extracted.
Since the second process generates the processing information such that at least one of the wavelength components that give the adverse effects to the properties of the molded component is selectively removed, processing of the surface shape of the second molding part, it is checked whether newly produced or the first molding part being reworked, can be performed more efficiently and accurately than the conventional method that uses a uniform contraction ratio.
In this manner, an efficient production of an injection mold that is suitable for producing a molded component that surely realizes designed properties is possible.
Here, the plurality of the wavelength components may include a first wavelength component and a second wavelength component.
In this case, the second wavelength component is extracted based on the surface shape of the cavity of the first molding part, and the first wavelength component is extracted based on the shape of the molded component. Alternatively, both the first and the second wavelength components may be extracted from one of the first molding part and the molded component. Further, alternatively, the first wavelength component may be extracted from the surface shape of the cavity of the first molding part, while the second wavelength component is extracted based on the shape of the molded component.
Further, in this case, the first wavelength component (the wavelength component extracted based on the surface shape of the cavity of the first molding part) may be set shorter than the second wavelength component (the wavelength component extracted based on the shape of the molded component).
In the first process, the first wavelength component may be extracted from shape errors along a first direction, while the second wavelength component is extracted from shape errors along a second direction that is different from the first direction. In this case, the first direction and the second direction may be set orthogonal.
In the first process, shape errors may be interpolated based on shape errors measured at a plurality of measuring points.
In the first process, a third wavelength component may be extracted in addition to the first and the second wavelength components, and the second process may be configured such that the processing information is generated in order to reduce at least one of the first, the second and the third wavelength components. Further, in this case, the first and the second wavelength components may be extracted from the shape errors along the first direction, while the third wavelength component is extracted from the shape errors along the second direction that is different from the first direction.
Further, the first wavelength component may be set as longer than 10 mm and obtained based on the shape of the molded component produced using the first molding part, and the second wavelength component may be set as shorter than 20 mm and obtained based on the surface shape of the cavity of the first molding part, while the third wavelength component is an error component of the radius of curvature (radius of curvature error) obtained based on the shape of the molded component produced using the first molding part.
Further, in the first process, a wavelength component obtained as a difference between a polynomial obtained from measurement values of the shape of the molded component and a designed polynomial, and a wavelength component obtained as a band-pass-filtered error between the measurement values of the cavity of the first molding part and a polynomial obtained from the measurement values may be extracted.
In the second process, the processing information by which the surface shape of the cavity of the second molding part is processed may be generated based on an amount of compensation (compensation amount) obtained using a compensation amount based on at least one of the wavelength components of the molded component produced using the first molding part, and using a contraction ratio of the molding material at least in one direction.
Where the compensation amount z is expressed as z=f(x, y) on an XYZ rectangular coordinate system, the compensation amount for the surface shape of the cavity of the first molding part can be expressed as one of zk=xe2x88x92f (xe2x88x92mx x, my y)/mz and zk=xe2x88x92f (mx x, xe2x88x92my y)/mz, where, mx, my, and mz are contraction ratios in X, Y and Z-directions, respectively.
The present invention may include a third process that processes the surface shape of the cavity of the second molding part, based on the process information generated at the second process. Here, the second molding part may be the same as or different from the first molding part that was used in generating the processing information.
In the third process, the surface shape of the cavity of the first molding part may be processed, and made the second molding part. That is, the second molding part may be the first molding part the surface of the cavity of which is reworked.
The third process may employ at least one of a cutting process by a single crystal diamond byte, and a polishing process where a polishing tool contacts the surface to be processed through an area that is smaller than 3 mm in diameter.
The injection mold of the present invention is produced according to the production method of the present invention.
The injection mold of the present invention is produced by reducing an amount of at least one of the wavelength components of the shape errors. As the result, a molded component produced using the injection mold surely realizes properties that are designed.
The molding method of the present invention is characterized by transcribing the surface shape of the cavity of the molding part of the injection mold, under predetermined molding conditions at which a shape of the molded component is stably obtained, using the injection mold of the present invention.
By the molding method, molding is performed by using the injection mold that is processed by the processing information that is configured to selectively reduce at least one of the wavelength components of the shape errors that adversely affect the properties of the molded component, under the predetermined molding conditions that stably provide the shape of the molded component. In this manner, the molded component that surely realizes the designed properties can be produced stably.
The designing apparatus of the present invention is configured to produce an injection mold that has a cavity of a predetermined shape, surface shape of the cavity being copied to a molding material in order to produce a molded component, and includes a shape inputting means, an error component extracting means and a processing information generating means.
The shape inputting means is configured to input at least one of the surface shape of the cavity of the molding part, and the shape of the molded component to which the surface shape is copied.
The error component extracting means extracts a plurality of wavelength components of shape errors, based on measurement.
The processing information generating means generates processing information such that, when the surface shape of the cavity of the molding part is processed using the processing information, at least one of the wavelength components extracted is reduced. In this manner, the process using the processing information realizes a more efficient production of a higher precision surface shape of the cavity of the molding part than the conventional process that is based on applying a uniform contraction ratio to allover the surface shape.
Therefore, according to the present invention, the injection mold that is suitable for producing the molded component that surely realizes the designed properties can be efficiently designed.
Therefore, according to the present invention, the injection mold that is suitable for producing the molded component that surely realizes the designed properties can be efficiently designed.
The present invention provides a computer program that is executed by a computer such that an injection mold that has a mold cavity of a predetermined shape, a surface shape of the cavity being copied to a molding material in order to produce a molded component, is designed. The computer program includes an extracting step that extracts a plurality of wavelength components of shape errors contained in at least one of the surface shape of the cavity of the molding part and the molded component produced by the injection mold, and a processing data generating step that generates processing data with which the surface shape of the cavity of the molding part is processed such that an amount of at least one of the wavelength components is reduced.
At the extracting step, the wavelength components of the shape errors contained in the molded component are extracted based on at least one of the surface shape of the cavity of the molding part and the molded component that copies the surface shape. Then, processing data is generated, at the processing data generating step, such that a process using the processing data reduces an amount of at least one of the wavelength components extracted. Since a wavelength component that adversely affects the properties of the molded component is selectively reduced by the present invention, a more efficient and a more accurate designing of the surface shape of the cavity of the molding part becomes possible, than by the conventional manner.
Accordingly, the computer program provided by the present invention realizes an efficient designing of an injection mold that is suitable for producing a molded component that surely realizes designed properties.
The present invention provides the production system that is configured to produce an injection mold that has a mold cavity of a predetermined shape, surface shape of the cavity being copied to a molding material in order to produce a molded component. The production system includes a processing information generating unit and a processing apparatus.
In the production system, a wavelength component of shape errors contained in the molded component, which adversely affects the properties of the molded component, is selectively reduced. The processing information may be transmitted to the processing apparatus through a network and the like.
The production system processes based on the processing information, such that a more efficient production of the injection mold is realized, the injection mold possessing a higher precision surface shape of the cavity of the molding part than the conventional system that applies a uniform contraction ratio.
In this manner, the present invention efficiently provides the production system of the injection mold that realizes designed properties.
The production system may also include a shape measuring unit that measures one of the surface shape of the cavity of the first molding part and the molded component produced by the first molding part. Results measured by the shape measuring unit are transmitted to the information generating unit via the network, and the like.
The present invention provides the molded component that is produced by copying the surface shape of the cavity of the molding part to a molding material using the injection mold.
Since the injection mold that is produced by selectively reducing a wavelength component that adversely affects the properties of the molded component, the molded component of the present invention can surely realize designed properties.
The present invention provides an optical component that is produced by copying the surface shape of the cavity of the molding part to a molding material using the injection mold.
Since the injection mold that is produced by selectively reducing a wavelength component that adversely affects the properties of the optical component, the optical component of the present invention can surely realize designed optical properties.
The optical component may include a plurality of sets of processing marks copied on the molding material.
In this case, the optical component may include a first set of the processing marks at a peripheral of an optical surface in a longitudinal direction, and a second set of the processing marks in a finer pitch than the first set of the processing marks at a predetermined angle in reference to the longitudinal direction in an area inside the first processing marks.
An absolute value of a shape error A of the optical component can be set within a range of 0.00001 xW less than =A less than =0.0005 xW, where A represents the absolute value of the shape error in a band-pass-filtered wavelength range between 0.5 D and 1.5 D, where D represents a diameter of an area of the light flux, the area having a light intensity greater than 1/e2, where 1 is the light intensity at the center of the light flux, and W represents a diameter of the light flux at a focal point when the light flux characterized by the diameter D is input.
In this case, an attenuation ratio of the band-pass filter can be set at smaller than xe2x88x9212 dB/ octave.
The present invention provides an optical system that includes an optical scanning system that scans a scanning object with a light beam, or a light flux, from a light source. The optical scanning system includes a deflection unit that deflects the light from the light source in a predetermined range of angles, and an optical unit that includes at least an optical component of the present invention in an optical path from the deflection unit to the scanning object.
Accordingly, the optical system uses the optical component of the present invention, which can realize designed optical properties, therefore, the optical system can perform an accurate scanning of the light from the deflection unit on the scanning object. As the result, the scanning accuracy of the optical system is enhanced.
Various applications of the optical system are conceivable. The optical system can make an image forming apparatus, wherein the scanning object is an image-bearing object on which an image is formed by scanning the light through the optical system, possibly further provided with a copying unit.